Beamforming for O-RAN-Based Cell-Free mMIMO Systems with Multiple CPUs

In this paper, we consider an Open RAN (O-RAN)-based cell-free massive multiple-input multiple-output (mMIMO) system with multiple central processing units (CPUs). In this system, to achieve high network performance, suppressing the inter-cluster interference (ICI) is important. To this end, we study the problem of maximizing the sum of data rates for user equipments (UEs) served by each CPU by optimizing the beamforming of O-RAN radio units (O-RUs). To solve this problem, we develop an effective algorithm, and show that our proposed algorithm significantly enhances performance in O-RAN-based cell-free mMIMO systems with multiple CPUs.